Study On Temperature Field And Effects Of Hollow High Pier

By the influence of solar radiation and environmental temperature, the concrete structure, which placed in the natural environment for a long time, induces time-varying non-liear temperature field, resulting temperature stress and deformation. Under the most unfavorable environmental condition, the stress caused by the temperature load, which can be comparable in magnitude to live load stress, contributes significantly to the cracking of the concrete structure.In this paper, a C++software to calculate the temperature field of concrete is developed by using finite difference principle, and reliability of the software calculation is verified through a concrete slab temperature field experiment. The vertical and horizontal temperature distribution of concrete slab is studied by comparing experiment and C++numerical simulation results. Then, sensitivity studies of different parameters of hollow high pier sidings are conducted in order to find out the general condition that the most unfavorable temperature field occurs, and reference values of the monthly maximum temperature difference of hollow high pier in different cities are provides. Finally, the temperature stress and deformation of hollow high pier under the most adverse temperature load are analysed through the finite element model of hollow high pier which is taking No.5 hollow high pier in Nanpanjiang River Bridge as the study object, and established by using the ANSYS finite element software. The main research results are as follows:(1) The internal temperature of the concrete structure with azimuth angle αn= 0° is a sine curve. The maximum temperature as while as the maximum temperature decay rate gradually decrease from the sun side surface to the inside. Besides, the time that maximum temperature appears is gradually lagged, and the lag time gradually increase with the decrease of the maximum temperature decay rate. The temperature gradient of concrete structure can be divided into two stages according to the heat transfer direction between the surface and the outside, namely the temperature gradient increases stage and the temperature gradient decreases stage.(2) The temperature field of hollow high pier siding is influenced significantly by the direct solar radiation. On one hand, the horizontal direct solar radiation mainly affects the average temperature, on the other hand, the surface direct solar radiation mainly affects the temperature gradient. Actually, the surface azimuth angle has influence on the intensity of surface direct solar radiation, as a result, the temperature gradient decreases with the increase of surface azimuth angle.(3) The temperature gradient of hollow high pier siding is influenced by air temperature, but not significant. When the air high temperature rise, the average temperature inside the hollow high pier increases. Otherwise, when the diurnal temperature range increases, the average temperature inside the hollow high pier decrease as while as the temperature gradient increases. Besides, under the low wind speed condition, the temperature gradient of the hollow high pier siding decreases with the increase of the wind speed.(4) The temperature field of hollow high pier siding has obvious regional difference. Generally, the maximum temperature differences inside the hollow high pier will be less in flat areas than in more mountainous regions, and less in cities than in rural area, and greater in cities than in industrial area. Across the country, in different provincial capital cities and municipalities directly under the Central Government, the maximum temperature difference inside hollow high pier generally occurs in winter or sping, but the discrepancy of the value is obviously.(5) The general condition, which a hollow high pier siding induces the most unfavorable temperature field, is that the surface direct solar radiation should be strong as while as the sunshine time should be longer, and the azimuth angle should be zero, and the temperature difference should be large, as while as the wind speed should be small.(6) The analysis results of hollow high pier in Nanpanjiang River Bridge show that the horizontal tensile stress caused by most unfavorable temperature load can reache 3.2MPa, and the vertical tensile stress in transition segment between the sidings and the solid caused by fixed constraint is even up to 4.2MPa. Along the bridge, the horizontal displacement at pier top caused by temperature load is up to 31mm.